This invention relates generally to apparatus for applying print to the exterior surfaces of flexible tubes and, more particularly, is directed to mechanisms for transfering such tubes onto and off of a mandrel assembly of such apparatus.
In general, a variety of machines for applying a decorative print to containers, such as tubes and the like, are known. Such machines generally include an infeed or conveyor assembly that transports the tubes to a positioning unit that receives the tubes and moves them into position for transfer to corresponding mandrels located on a rotatable mandrel wheel. After the tubes are received on the corresponding mandrels, the mandrels are rotated into position for the printing operation, whereby a printing blanket is brought into contact with each of the tubes, to place a decorative finish on the outer cylindrical surfaces thereof. Thereafter, the mandrels bearing the tubes are moved to another location where the tubes are dried and then to still another location where a coat of varnish is applied to the decorated outer surface of each tube to finish the decoration thereon. The tubes are then removed onto a pin chain and the varnish is cured at a subsequent station, for example, by ultraviolet light.
As an example, U.S. Pat. No. 3,097,593 discloses apparatus for printing tubular sleeves. With this patent, after the flexible, plastic tube is dropped into a hopper, a first pusher member pushes the tube partially onto a mandrel. At the next rotational position of the mandrel wheel, a locating member having a ring engages the end of the tube to push the tube further onto the mandrel into a precise location thereon. The pushing operations are connected with and timed with the indexing mechanism for the mandrel wheel.
U.S. Pat. No. 3,250,213 discloses another tube decorating machine. With this patent, the tubes are transferred by a conveyor belt to respective of pockets or slots of a cylindrical shaped body portion which is rotated such that a first pusher pushes the tubes partially onto the mandrels and then at a second intermittent position, a second pusher completely pushes the tubes onto the mandrels.
U.S. Pat. Nos. 2,175,560; 2,288,617; 2,796,164; and 2,800,872 each disclose a single pusher rod for pushing the tubes onto the mandrels.
However, because the tubes are generally made of a plastic material, and are therefore flexible, the tubes tend to distort or get out of round, particularly during handling thereof. For example, U.S. Pat. No. 3,097,593, discussed above, includes two fingers which pick up the leading tube, and then drop such tube into the entrance hopper. However, the fingers tend to greatly distort the shape of the tube, as shown in FIG. 8 of the patent. As a result, the tube may exhibit an out-of-round configuration. This, in turn, may give rise to difficulties when the first pusher member attempts to partially push the tube onto a mandrel. U.S. Pat. No. 3,250,213, discussed above, in fact, specifically refers to the elliptical shape that the tubes often assume, at Column 4, Lines 43-46 thereof. Accordingly, with this patent, to ensure proper seating of the tubes on the mandrels, the ends of the mandrels must be modified. This, of course, results in greater complexity of the machine, since each mandrel must be modified and, in any event, is not a completely satisfactory solution.
With respect to the transfer of the tubes off of the mandrels, U.S. Pat. No. 3,097,593 includes a yieldably mounted star wheel having pockets and which closely engages around a portion of the outer periphery of each mandrel behind the container body thereon, as each mandrel is rotated to a predetermined position. The star wheel is connected through a linkage mechanism to a cam which rotates in time with the other moving parts of the machine. The cam causes a slide bar of the linkage mechanism, and thereby the star wheel connected thereto, to reciprocate at the proper time to strip the printed body entirely off the mandrel to a suitable point of discharge, such as a pin conveyor chain.
In a similar context, U.S. Pat. No. 4,089,294, for use with aluminum tubes that may not be dried, provides a two legged hanger for removing the tubes from a tube holder. U.S. Pat. No. 1,910,713 discloses a slide having a hook end which engages the rear edge of the tube and pulls it off the respective pin. See also U.S. Pat. No. 2,835,371 (FIGS. 9-12). Lastly, U.S. Pat. No. 1,892,545 teaches a stripper plate surrounding each conveyor pin for removing the sleeves from the pins, although the pins are arranged in the vertical direction.
The above exit transfer assemblies are not completely satisfactory, because of the complexity thereof and the problems with timing.